This CoriantTypesTestSignalConfig value (default NONE) turns on the test-signal function for a 10G WAN PHY client port framed as SONET and configures whether it applies toward the client or line side. An administrator activates this during turn-up or troubleshooting to substitute a known test pattern for live traffic and check for errors without needing an external test set physically inserted upstream. For example, enabling test-signal generation toward the line side on 10G WAN SONET lets a technician confirm the trunk-facing optics and framing are error-free before re-enabling the real client traffic mapping.